Module 2.1 - Bonding in Ceramics Flashcards
Attractive forces in ceramics are due to what?
Nature of bonding between atoms.
Repulsive forces in atoms are due to what?
Interactions between the negatively charged electron clouds.
What a system of 2 atoms is in equilibrium, what does this entail about the net force?
It has reached the point where the net force is 0, and the atoms are in critical distance.
Equilibrium spacing occurs when?
Net force between two atoms is 0, and the bond energy is at a minimum.
When is the bonding energy Eo at a minimum?
At the equilibrium spacing or when net force between two atoms is 0.
When is the bonding energy Eo at a minimum?
At the equilibrium spacing or when net force between two atoms is 0.
What are two types of bonds? Differentiate them.
Primary - chemical bonding
Secondary - Van der Waals
How do secondary bonds occur?
they arise due to induced dipoles (can be temporary or permanent)
What is the most electronegative element?
Fluorine
When a bond has a higher electronegativity value, what does this entail about its ionic character?
More electronegative = more ionic character
Do all ionic bonds have some covalent character?
Yes, all do.
How come a purely ionic bond cannot exist?
Complete charge transfer is highly unfavorable, and this is because of the increase in kinetic energy.
Ionic bonding is the _______ between electrons, while covalent bonding is _______ between electrons.
- Transfer
- Sharing
What facilitates the transfer of electrons in ionic bonding?
Coulombic (electrostatic) attraction between the anion of one element, and the cation of one element.
Ionic bonding causes materials to have a high melting point, to be hard and brittle, and to be electrically and thermally insulative. True or false?
True.
What is the lattice energy?
Summation of all bonding energies with respect to a central atom.
For electrostatic interactions, for the FIRST nearest neighbors, the central anion is attracted to the six neighboring cations at what distance?
r0
For electrostatic interactions, for the SECOND nearest neighbors, the central anion is attracted to the six neighboring cations at what distance?
(sqrt of 2)(r0)
For electrostatic interactions, for the THIRD nearest neighbors, the central anion is attracted to the six neighboring cations at what distance?
(sqrt of 3)(r0)
Covalent bonding occurs between atoms that?
Have small differences in electronegativity
Covalent bonding can be very strong or very weak. True or false?
True
It is possible to predict mechanical properties through bonding alone. True or false?
False, it’s difficult to predict mechanical properties from bonding alone.
